Folding machines for large engineering documents ("prints") typically comprise two distinct sections, a fan-folder and a cross-folder. The fan-folder transforms the incoming document into a rectangular packet as shown in FIG. 1, in which the longer dimension (A) is the printer roll width, and the shorter (B) is the desired panel width (typically 81/2 inches in the USA, 210 rnm in other countries). The fan-folder in most document folding machines is capable of producing a tightly folded packet with sharp creases shown as (B) in FIG. 2 and few undesirable artifacts. It is in the cross-folder that problems arise if the packet is not positively controlled in the transition from fan-folder to cross-folder. If the panels of the fan-fold packet are allowed to separate, or so-called "billow-out", there is the likelihood that a false, or a double-fold (D) may result as the packet is pulled into the cross-folder through fold rollers under pressure. Another possible consequence is deflection of the entire packet, resulting in cross-folds not orthogonal to the edges of the fan-fold packet. There is, therefore, a need in the art for a device which avoids these problems.